Ever since the introduction of the fiber optics technology, the optical fiber has proven to be a most versatile and promising means of transmitting data and information. Recent advanced developments in fiber optics sensor technology have spurred considerable research on embedding optical fibers and optical fiber sensors in various materials and structures. Studies have been conducted on embedding optical fibers in graphite-epoxy composites, plastics, concrete, and solder metals with relatively low melting temperature of 190.degree. C.
Optical fibers and sensors embedded in metals with much higher melting temperatures and strengths are desirable in numerous applications. For example, if metal-embedding were possible, an optical fiber sensor can then be cast into the cylinder head of an internal combustion engine to monitor its performance. In addition, metal-embedded fibers are applicable to connectors and feedthroughs in, for example, vacuum systems, undersea vehicles, undersea repeaters, chemical processing plants, and steam power plants. Metal-embedded fiber sensors may also find application in smart structures, such as aircraft wings and fuselages, ships, spacecraft, bridges, and buildings.
Previous attempts to embed optical fibers in metals with high melting temperatures have all resulted in failure. The fragile fibers invariably break either at or near the air-metal interface. The fiber breakage has been attributed to the stress inflicted on the fiber by the contraction of the surrounding metal as it cools from its melting temperature to room temperature. Therefore, it is obvious that resolution of the fiber breakage problem in embedding optical fibers in metals has broad implications. The present invention is a novel and unique solution to this problem.